Industrial furnace



Dec. 31, 1968 J. J. MARTIN 3,418,996

INDUSTRIAL FURNACE Filed Feb. 28, 1967 Sheet of 2 INVENTOR I l/dual J'h ker- 13 ATTORNEY Dec. 31, 1968 J. J. MARTIN 3,418,996

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INVENTOR United States Patent Office 3,418,996 Patented Dec. 31, 1968 ABSTRACT OF THE DISCLOSURE A composite grate for use in industrial furnaces, comprising relatively movable sections and springs or weights for urging the sections apart and against an enclosure, such as the furnace walls. The springs or weights yield in response to thermal expansion of sections. By tending to move the sections apart, the springs or weights prevent the formation of gaps between and around the sections of the grate.

Background of the invention The present invention relates to industrial furnaces in general, and more particularly to improvements in the construction and mounting of grates in such furnaces.

The grates of large industrial furnaces normally consist of two or more sections or panels. Each section comprises grate bars whose ends are carried by fixed supporting members extending longitudinally or transversely of the area surrounded by the fire-resistant charge-receiving enclosure. In a continuous type furnace, the grate bars form a conveyor which travels through the enclosure. Alternatively, two or more groups of grate bars are moved relative to each other to shift the charge from the one to the other end of the hearth. 1

In order to account for thermal expansion of grate bars in response to exchange of heat with injected hot air and/or the charge, the sections of the grate must he installed with sufficient clearance which is selected in such a way that the sections cannot jam or stick at the highest temperatures which are expected when the furnace is in actual use. Of course, the gaps between the sections of the grate and between the grate and the surrounding enclosure are more pronounced when the furnace is idle as well as when the furnace is operated at less than full capacity, i.e., when the grate bars are cOld or are heated to less than a maximum permissible temperature. This leads to consideralble losses because the ingredients of the charge can descend through the gaps between or around the grate sections or enter such gaps to prevent thermal expansion of grate bars in response to heating. Furthermore, portions of the charge can be ignited around the grate or in the space below the grate which is undesirable in most types of industrial furnaces.

Accordingly, it is an important object of my invention to provide an industrial furnace with a novel and improved multi-section grate and to construct and assemble the grate in such a way that its sections invariably prevent uncontrolled passage of the charge, not only between but also around the individual sections.

Another object of the invention is to provide a grate whose sections invariably form an uninterrupted barrier across the area surrounded by the enclosure of an industrial furnace, irrespective of the temperatures which prevail in such enclosure and irrespective of the wear upon the sections of the grate.

A further object of the invention is to provide a grate of the above outlined characteristics which can be utilized with equal advantage in many types of industrial furnaces, including batch-, continuous-, heat recoveryand other types.

A concomitant object of the invention is to provide a grate which can comprise two or more sections and wherein the clearances or gaps between such sections as well as between the sections and the surrounding parts of the furnace are either eliminated or bridged in such a way that the grate prevents uncontrolled passage of charge or interference by portions of such charge with expansion or contraction of grate sections.

An additional object of the invention is to provide a composite grate with devices which prevent entry of dirt or other foreign matter between relatively movable sections of the grate,

Summary of the invention One feature of my invention resides in the provision of an industrial furnace which comprises an enclosure or outer wall structure surrounding an area for reception of a charge which is to be heated, a grate installed in the enclosure to extend across the aforementioned area and comprising at least two sections at least one of which is movable with reference to the other section in response to expansion and contraction resulting from changes in temperature, and compensating means for yieldably biasing the one section against the enclosure. The compensating means is arranged to yield in response to thermal expansion of the one section and may comprise one or more helical or otherwise 'configurated springs and/or one or more weights. In the latter instance, the compensating means also comprises motion transmitting means arranged to move the one section away from the other section in response to downward movement of the Weight.

For example, the grate may comprise three sections one of which is disposed between the other two sections, and the other two sections then abut against or are fixed to the enclosure. The compensating means comprises springs and/or weights for biasing the one section away from the other two sections whereby the other two sections are automatically compelled to remain in abutment with the enclosure if they are not aflixed thereto.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved furnace itself, however, both as to its construction and the mode of assembling the same, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

Brief description of the drawing FIG. 1 is a somewhat schematic fragmentary transverse vertical sectional view of an industrial furnace which embodies one form of my invention;

FIG. 2 is an enlarged transverse vertical sectional view of a detail of the furnace shown in FIG. 1;

FIG. 3 is an enlarged transverse vertical sectional view of a portion of a modified furnace wherein the sections of the grate are biased apart by gravity-operated compensating means; and

FIG. 4 is a similar transverse vertical sectional view of a portion of athird furnace wherein the compensating means comprises spring-biased expanders.

Description of the preferred embodiments FIG. 1 illustrates an industrial furnace which comprises an enclosure E surrounding an area serving to receive a charge which is to be heated. The walls of the enclosure normally consist of refractory material and are assumed to form part of an under firing furnace. The grate of this furnace is installed in the enclosure E and extends in a horizontal plane across the charge-receiving area. It comprises three relatively movable sections or panels I, II and Ill. Merely for the sake of comparison,

the leftmost section I is shown as being mounted in accordance with the presently prevailing practice, i.e., in such a way that when its grate bars 1 contract in response to cooling, a gap or crack 11 will develop between its lefthand marginal portion and the adjoining wall of the enclosure E. An important object of my invention is to prevent the formation of such gaps or cracks irrespective of the temperature of grate bars 1. The gap 11 will develop if the right-hand wall member 2 of the section I is rigidly affixed to its supporting column C.

In accordance with a first embodiment of my invention, the sections of the grate are mounted in a manner as shown in greater detail in FIG. 2. Thus, the right-hand wall member 2 of the median section II is provided with an extension or rail 2A received with requisite clearance in a slot 2B provided in the top portion of the adjoining supporting column C The left-hand wall member 2a of the section III is slidably telescoped into the wall member 2 of the section 2 and the furnace further comprises compensating means including prestressed horizontal helical expansion springs 3 which are interposed between and tend to move the wall members 2, 2a of FIG. 2 away from each other. In this way, the left-hand wall member 2a of the section 11 (see FIG. 1) will be caused to penetrate deeper into the adjoining wall member 2 of the section I, and the right-hand wall member 2 of the section II will move toward the section III if the section II expands in response to heating. Since the wall member 2 of the section I is movable with reference to its column C in the same way as shown for the wall member 2 of FIG. 2, expansion of the section II will result in further compression of springs 3 between the sections I, II and the left-hand marginal portion of the section I will invariably abut against the adjoining wall of the enclosure E to prevent the formation of a crack 11. At the same time, the right-hand wall member 2a of the section III will penetrate deeper into .a wall member 2' which is shown as being firmly mounted in the adjoining wall of the enclosure E. The wall member 2 can be said to constitute a permanently anchored fourth section of the grate.

In its simplest form, the grate of my invention may comprise only two sections, for example, the wall member 2' and the section III whereby the latters left-hand wall member 2a abuts against the left-hand wall of the enclosure E shown in FIG. 1. The compensating springs 3 permanently bias the section III toward the left-hand wall of the enclosure E, irrespective of the temperature which prevails in the charge-receiving area. In the absence of sections I and II, the section III will bear directly against the enclosure E. Of course, the grate may comprise the sections 2, III and II or the sections I, II, III whereby the right-hand wall member 2a of the section III can bear directly against the enclosure E, the same as the left-hand marginal portion of the section I.

Since the wall members 2, 2a of adjoining sections are slidably telescoped into each other, the grate will not develop any gaps, regardless of whether the furnace is cold or in actual use. It is further clear that the left-hand marginal portion of the section I shown in FIG. 1 may comprise a wall member 2a which is then telescoped into a wall member 2' or bears directly against the adjoining portion of the enclosure.

The wall members 2, 2a of the sections IIII preferably comprise two or more unit lengths arranged end-to end and biased apart by springs so as to be movable with reference to each other in response to thermal expansion or contraction.

FIG. 3 illustrates the compensating structure of a modified furnace. The wall members 102, 102a form part of two adjoining grate sections and are slidably telescoped into each other. The compensating structure comprises a horizontal pivot 5 mounted at the upper end of a connecting rod 6 and carrying at least one but preferably two two-armed motion transmitting levers 4, 4a which are rockable on the pivot 5 and each of which is inclined with reference to the (horizontal) direction of displacement of wall members 102, 102a relative to each other. The lower arms of the levers 4, 4a extend into shallow notches 9 provided at the inner sides of the wall members 102, 102a and the pivot 5 is biased downwardly by a stressed helical spring 7 which operates between an adjusting nut 18 on the connecting rod 6 and a horizontal guide portion 17a of the supporting column 17. The extensions 102A of the wall members 102, 102a are received with clearance in a slot 102B of the column 17.

The spring 18 urges the rod 6 and pivot 5 downwardly whereby the arms of the levers 4, 4a urge the wall members 102, 102a away from each other. The spring 7 will yield if the wall member 10211 penetrates deeper into the wall member 102 in response to thermal expansion of the grate sections.

The compensating structure of FIG. 3 can be operated by gravity if the spring 7 is replaced with a mass or weight G (shown by phantom lines) which is then suspended on the connecting rod 6 or directly on the pivot 5. Of course, the weight G can be employed in addition to (not as substitute for) the spring 7.

The adjusting nut 18 is in mesh with the rod 6 and is rotated when the operators wish to change the initial bias of the spring 7. The weight G may consist of several separable portions so that, by removing or adding one or more portions, the operators can bring about the same result as with rotation of the nut 18.

The compensating structure of FIG. 3 further comprises an indicating device which furnishes readings regarding the thermal stressing of grate sections. This indicating device comprises an index 8 which is afiixed to the connecting rod 6 and a suitably graduated scale 10 which is aflixed to a stationary part of the furnace. The position of the scale 10 and index 8 can be reversed, and it is equally possible to install one of these elements on the pivot 5, on the weight G or on any other part which shares the movements of the pivot 5 with reference to the supporting column 17. The feature that the parts 7, 8, 10, 18 (and G) are installed below the grate is of considerable advantage because such parts are protected from cinder and are properly cooled if the furnace of FIG. 3 is of the under firing type. The pivots 5 and levers 4, 4a are adequately protected by the telescoped wall members 102, 102a.

The nut 18 can be replaced by a handwheel or by a winged nut. The position of notches 9 and the inclination of the levers 4, 4a are such that the spring 7 is free to expand when the grate sections including the wall members 102, 102a contract and that the spring 7 is compelled to contract if the grate sections expand. The grate sections are assumed to be located in a substantially horizontal plane and their expansion or contraction will depend on changes in temperature which prevails in the enclosure (not shown in FIG. 3). The nut 18 and/or the weight G is preferably accessible at all times so that the personnel in charge can regulate the bias of the compensating structure. By observing the position of the index 8, the operators can regulate the inflow of cooling air which can be admitted at one or more points.

It is clear that the index 8 and scale 10 can be used with equal advantage in the furnace of FIGS. 1 and 2. For example, the scale 10 can be fixed to the column C and the index 8 can be attached to the section II.

Referring finally to FIG. 4, there is shown a portion of a third furnace including a grate having two sections I, II which comprise wall members 202, 202a. These wall members define between themselves two longitudinally extending gaps or clearances which are bridged by two arcuate expanders 12, 12a forming part of a compensating structure. The latter further includes one or more prestrcssed helical springs 15 which operate between and tend to move the expanders 12, 12a away from each other. The spring 15 shown in FIG. 4 surrounds a guide rod 14 passes through an opening 12A in the lower expander 12a and is afiixed to a sleeve carried by a portion 16 of a supporting column 217. The latter carries the wall members 202, 202a with sufiicient freedom of movement toward and away from each other.

The upper expander 12 is provided with downwardly extending guide portions or skirts 13 which can engage the wall members 202, 202a. It is clear that the curvature of the convex external surfaces must be selected in such a way that the wall members 202, 202a are movable away from each other (in response to expansion of the spring 15) or toward each other (in response to thermal expansion of grate sections 1 and II).

The wall member 202 or 202:: of FIG. 4 can be fixedly secured to the column 217 if the other marginal portion of the section I or II is immovably secured to the enclosure. The same holds true for the grate of FIG. 3.

Thus, it is often sufiicient to utilize a grate with a single L structure In comprises springs which bias the two portions of the section II away from each other.

The wall members of the grate sections and/ or the wall members of portions of a grate section can be provided with heat dissipating fins, ribs or analogous projections.

The bias of the compensating means is preferably selected in such a way that the compensating means prevents the formation of gaps even if the sections of the grate undergo extensive wear or corrosion after long-lasting use in an industrial furnace. For example, the springs 3, 3 and the spring or springs of the compensating structure 1a shown in FIG. 1 should prevent uncontrolled descent of cinder into the space below the grate.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features which fairly constitute essential characteristics of the generic and specific aspects of my contribution to the art and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims:

1. An industrial furnace, comprising an enclosure surrounding an area for reception of a charge which is to be heated; a grate installed in said enclosure and extending across said area, said grate comprising at least two Sections at least one of which is movable with reference to the other section in response to expansion and contraction resulting from changes in temperature; and compensating means for yieldably biasing said one section away from the other section toward said enclosure, said compensating means being arranged to yield in response to thermal expansion of at least said one section.

2. A furnace as defined in claim 1, wherein said sections comprise adjoining wall members and said compensating means comprises means for biasing the Wall member of said one section away from the other wall member.

3. A furnace as defined in claim 2, wherein said compensating means comprises resilient means.

4. A furnace as defined in claim 3, wherein said grate is disposed in a substantially horizontal plane and wherein said resilient means comprises springs interposed be tween said wall member.

5. A furnace as defined in claim 2, wherein said cornpensating means comprises at least one weight and motion transmitting means arranged to move the wall member of said one section away from the other wall member in response to downward movement of said weight.

6. A furance as defined in claim 5, wherein said wall members are slidably telescoped into each other and wherein said motion transmitting means comprises a p vot disposed intermediate said wall members, a connection between said pivot and said weight for urging the pivot downwardly, and a two-armed lever rockably mounted on said pivot at an angle to the direction of movement of said one wall member, each arm of said lever engaging one of said wall members.

7. A furnace as defined in claim 2, further comprising means for indicating the position of said one wall membet.

8. A furnace as defined in claim 7, wherein said indictating means comprises an index element and a scale element, one of said elements being fixed and the other element being arranged to share the movements of the wall member of said one section and to thereby change its position relative to the other element.

9. A furnace as defined in claim 2, wherein said compensating means comprises expander means disposed intermediate said wall members and movable in a predetermined direction to thereby vary the distance between said wall members, and means for biasing said expander means in said predetermined direction.

10. A furance as defined in claim 9, wherein said expander means comprises a pair of expanders at least one of which is movable away from the other expander in said predetermined direction, said wall members defining between themselves a pair of gaps and each of said expanders being positioned to bridge one of said gaps.

11. A furnace as defined in claim 10, wherein said last mentioned biasing means comprises at least one helical expansion spring operating between said expanders and further comprising elongated guide means surrounded by said spring and extending through an opening provided in said other expander.

12. A furnace as defined in claim 10, wherein said one expander is provided with skirt means arranged to engage said wall members.

13. A furnace as defined in claim 1, at least one of said sections comprises a plurality of relatively movable portions and additional compensating means for yieldably biasing said portions away from each other.

14. A furnace as defined in claim 1, wherein said other section is afiixed to said enclosure.

15. A furnace as defined in claim 1, wherein said grate further comprises a third section interposed between said first mentioned sections, said compensating means comprising means for biasing said third section away from each of said first mentioned sections.

References Cited UNITED STATES PATENTS 2/1961 Rivers 126174 7/1967 Milligan 1587 

